Yo and welcome to dreamviews!
WILD has nothing to do with SP, so don't worry about it, and you don't really need to stay still or sleep in certain position, you just need to fall asleep while being aware.
It sounds like you have reached hypnagogic state but haven't gotten any further, maybe you were trying too hard with visualizing and just got too awake? Also, "kept telling that body going to sleep", it's better to not think about your physical body during WILD, that also might be the cause that got you too awake.
And also, check out this tutorial: WILD , which describes WILD process in-depth.
Good luck!